1. Field of the Invention
The present invention relates generally to dental compositions containing polymerizable compounds and nanometer-sized filler particles. The dental compositions can be applied as a polishing, sealant, bleach guard or other coating to the surfaces of dental restorations and teeth. The composition is cured to provide a durable and smooth coating. This improves the luster and aesthetic appearance of the restorations and teeth.
2. Brief Description of the Related Art
Dental professionals use polishing compositions (or varnishes) to coat surfaces of dental restorations and natural teeth. By the term “dental restoration,” as used herein, it is meant any material used to restore or replace lost tooth structure, teeth, or oral tissue including, but not limited to, fillings, inlays, onlays, veneers, crowns, and bridges.
For example, a dental practitioner may “fill a cavity” in a tooth with a composite filling material. Upon completing this step, the filling may have a relatively rough and uneven surface. So, the practitioner finishes the surface of the filling using high-speed dental burs. Then, the practitioner applies a polishing composition to the finished filling surface. The polishing composition provides a hard and smooth coating over the restoration. The finished restoration has a shiny and glossy appearance.
The dental industry is constantly looking to develop new polishes (or varnishes) that can be applied to the surfaces of restorations and teeth. For example, Pflug et al., U.S. Pat. Nos. 6,399,037 and 6,693,037 disclose dental materials including varnishes, sealants, and bonding agents containing nanoscale filler particles having a primary particle size of 1 to 100 nm. Suitable particles that can be used to prepare the nanoscale fillers are described as ground glass, ground quartz, highly dispersed silica, zeolite, laponite, kaolinite, vermiculite, mica, ceramic metal oxides, alumina, pyrogenic silica, sparingly volatile oxides of titanium, zirconium, germanium, tin, zinc, iron, chromium, vanadium, tantalum, and niobium. A sol of the filler particles in an organic solution is first prepared. The particles are treated with a silanizing agent so they can form a stable, low viscosity sol (about 1 Pas). After the particles have been dried, they are mixed with polymerizable monomers under high shear. The '037 patents describe the resulting dental material as having improved abrasion-resistance and surface-hardness. The dental material can be applied as a thin film.
Jia, U.S. Pat. No. 6,730,715 discloses curable dental compositions that can be used as cavity fillings, adhesives, sealants, luting agents, cements, orthodontic bonding materials, or restoratives. The composition includes acrylate and methacrylate monomers as well as a co-curable phosphoric acid ester. A curing system comprising polymerization initiators and accelerators is present in the amount of 0.01 to 5 weight percent. Water is added to the composition in the amount of 1 to 50 weight percent.
Stannard et al., U.S. Pat. No. 6,797,767 discloses polymerizable composite materials that can be used as restoratives, bonding agents, and adhesives. The material comprises at least one multifunctional acid containing monomer such as Bis-2(methacryloxy)ethyl phosphate; a non-reactive filler such as micron or submicron-sized particles of silica; a polymerization system capable of being activated by light to polymerize the composite material; and water. The composite material is applied to the tooth and then is set or cured by exposing the material to visible light.
Fukushima et al., U.S. Pat. No. 6,818,679 discloses a photopolymerizable dental composition that can be applied to the surface of crowns, fillings, and dentures. The composition comprises: a) a polyfunctional acrylate, b) a volatile (meth)acrylate compound, c) a fluoroalkyl group constituted of at least one fluorocarbon-containing (meth)acrylate compound, and d) an acyl phosphine oxide-based polymerization initiator. The composition is cured upon irradiation with visible light. The resulting cured coating is colorless and transparent with good durability, abrasion resistance and resistance to discoloration according to the '679 patent.
Zhang et al., U.S. Pat. No. 6,899,948 discloses dental materials comprising a hardenable resin and “nano-sized” silica particles dispersed within the resin. By “nano-sized,” it is meant that the silica particles have an average diameter size of less than 200 nm. The nano-sized silica particles are further described as being discrete and non-agglomerated and in a dry powder form. The dental materials can be used as adhesives, crowns, fillings, cavity liners, cements, orthodontic devices, prostheses, and sealants according to the '948 patent.
Suh et al., U.S. Pat. No. 7,081,485 discloses a dental composition comprising a multiacrylate compound and a photo initiator that can be light-cured by a curing light or light box system. The multiacrylate compound comprises at least five acrylate functionalities per molecule; and the composition does not comprise methyl methacrylate. The photo initiator is present at a concentration of at least about 6 weight percent. The composition can further contain fillers, nanofillers, and glass particles. Upon curing, the composition forms a coating having a surface lacking an oxygen inhibition layer. The composition can be used as dental coatings and sealants.
Although some of the foregoing dental compositions are generally effective in improving the luster and aesthetic appearance of the restoration and tooth, they have drawbacks and there is a need for an improved dental polishing composition.
One disadvantage with traditional polishing compositions is that the surface of the tooth must be pre-etched before the composition can be applied thereto. The etching step is not only time consuming but certain patients also are very sensitive to the acid etchants used on the tooth surface. Therefore, dentists are looking for a one-step dental polish that will work for restorations and tooth enamel surfaces. Dentists would be interested in such a dental polish because it could be applied without first acid-etching the restoration or tooth surface.
Furthermore, some traditional dental polishes have poor stain-resistance. Discolorations and stains may form on the tooth surfaces due to ingestion of coffee, tea, soda, or other food and beverages. An improved polishing composition that can provide a protective and durable film coating having high stain-resistance is needed in the dental market. Compositions having high stain-resistance could be applied to bleached teeth to protect the whitened surfaces.
Another problem with conventional polishing compositions is their poor wear-resistance. As the coating of traditional polishing composition wears away, the underlying restoration may lose its shine and luster. This can lead to the restoration having a dull surface and non-aesthetic appearance. In such instances, the patient must make periodic dental office visits so the dental practitioner can polish the surface of the restoration and restore its shine. Polishing the restoration can be a relatively lengthy procedure requiring different dental instruments and polishing pastes. Eliminating this polishing step would be a benefit to both the patient and practitioner. Accordingly, there is a need for a polishing composition having wear-resistance that can be applied over dental restoration and tooth surfaces. The polish should be capable of providing a protective and durable coating having high scratch/abrasion resistance.
The present invention provides dental composition having the above described desirable properties as well as other benefits and advantages. These include, for example, 1) the capability of being cured by multiple light sources including light emitting diode (LED) and halogen curing lights, 2) low viscosity which makes it easier for a practitioner to apply the composition onto the targeted area, and 3) a less yellowish colored appearance so the composition does not change the color of the underlying substrate. The dental compositions of this invention can be applied as a polish, sealant, bleach guard or other coating material to the surfaces of dental restorations and teeth.